This is latest summaries for episodes i found and some scans possibly spoilers:

Turn 16- Union of Nations, Resolution No.1 「超合集国決議第壱號」 , July 27th
From Newtype
The plan for founding a union of nations to stand against Britannia is realized by uniting 47 countries together, centered on the United States of Japan and the United States of China. As a result, the world is divided into two: Britannia and the Union of Nations. The world situation comes to a new phase.

From Animedia
The plan of Union of nations has realized. 47 countries ratified this, centered on the United States of Japan and the United States of China. Therefore, the world faces a new phase through totally weakening EU and dividing the world into two: Britannia and the Union of Nations. And the first resolution made in the highest council is...

Keywords from newsletter
Prepare to pay the consequences for challenging the Knight of Rounds.

Turn 17- The Taste of Soil 「土 の 味」 , August 3rd
From Newtype & Animage
In Area 11, the battle between the Black Knights and the strongest force of Britannia army is about to begin. At this time, to accomplish a certain purpose, Lelouch heads toward the Kururugi Shrine, where Suzaku awaits alone. Holding all kinds of thoughts in their confrontation, what is the destiny waiting for them?

From Animedia
Area 11 turned into a battlefield again. The battle between the Black Knights and the strongest force of Britannia army is about to begin on this land. At this time, however, Lelouch visits Kururugi Shrine by himself. His purpose is the thought that "right now, the only one who can save Nunnally is Suzaku". Lelouch and Suzaku meet again in the place of their memories.

Keywords from newsletter
Aren't you the man who bring miracles? Zero!
「君は奇跡を起こす男、ゼロなんだろう！」
(The "you" here is "kimi". Usually people who use "boku" as "I" would use "kimi" as "you". Sometimes "watashi" people would also use it, depending on situation. So this one is a little hard to guess.)

Turn 18- Tokyo Decisive Battle, The Second
Schenizel knows that Zero is Lelouch.
Having the Union of Nations backing them up, the Order of the Black Knights begins the decisive battle in Tokyo Settlement.

Turn 19 - Betrayal and Brotherhood 「裏切り と 兄弟」
Large casualties in the battle of Tokyo Settlement.
As if to pierce through this confusion, a Britannia special envoy visits the Ikaruga. Who may this person be?

Turn 20 - Emperor Assassination 「皇帝 暗殺」
From Newtype
Lelouch, driven into predicament, escaped thanks to Roro. However, what's left for him is isolation.

From CompAce
Alternative title: Emperor Assassination 「皇帝 暗殺」
Lelouch got out of a tight fix thanks to Rolo. However, there is only one road that he should tread... Is the world facing a new phase?

Keywords from newsletter
I want to know if you're still our ally.「あなたが今でも私たちの味方なのか知りたくって」
(Note: This line is in feminine form. So it should be from a female. Although I wouldn't rule out Kanon. XD)

Turn 21- Connection of Ragnarok 「ラグナレク の 接続」 , Aug 31
From Newtype
Area 11 is in huge chaos. In Lancelot Albion, Suzaku challenges a fight. The gentleness before isn't there anymore. What is the woeful determination that made Suzaku fearless against any opponent?

Turn 22- Emperor Lelouch 「皇帝 ルルーシュ」 , Sept 7th
Lelouch uses the balance between the forces that separates the world into two: UFN and Britannia.
The stage in his consideration is the place which was made into the neutral zone of the two countries, and a place of his memories.

Turn 23- Schneizel's Mask(シュナイゼル の 仮面) , Sept 14
From Newtype
Lelouch is suffering from having to become enemies with his beloved sister, Nunnally. To make him remember his original goal, Suzaku throws harsh words at him, and heads off towards the battlefield alone.

From Animage
Nunnally lives and shows up in front ot Lelouch as the worst enemy. Schenizel is indeed a fearsome tactician. Facing Lelouch who is in dilemma, what will Suzaku do? For control of the world, two genius conflicts in the sky over Mt. Fuji.

From Animedia
The person Lelouch loves most shows up infront of him as the worst enemy. Schenizel is indeed a fearsome tactician. While Lelouch is suffering from this, Suzaku will... For control of the world, two genius conflicts in the sky over Mt. Fuji.
It's for accomplishing Zero Requiem...

Turn 24- Sky of Damocles(ダモクレス の 空) , Sept 21
From Newtype
Lelouch is stuck in a difficult battle against the enemy vessel Damocles, which is heavily equipped with FLEIJA, the bomb that erased the empire capital Pendragon.

From Animage
(first half is the same as Animedia)
In the skies, Lelouch confronts Nunnally, and Suzaku confronts Kallen.

From Animedia
FLEIJA, the bomb that wiped out the empire capital Pendragon in a matter of minutes, is now massively equipped on the sky fortress Damocles as arms for the decisive battle. If Schenizel succeeds in his plan, the world is as good as his.

Turn 25 - 「Re:」, Sept 28
From Newtype
(blank)

From Animedia
Zero Requiem. It's all for the promise between Lelouch and Suzaku.
Farewell Lelouch. Is this the last day of Zero?
Good bye Suzaku. Farewell war time. And then…
Note: in the original text, they used "saraba" for Lelouch and war time, and "sayonara" for Suzaku. I wonder if this has a meaning to it.

From Animage
Zero Requiem. It's all for the promise between Lelouch and Suzaku.
Farewell Lelouch. Farewell Suzaku. What will become of their fate?

WARNING! THE FOLLOWING SPOILERS MAY HURT UR FEELINGS AND MOOD TO WATCH CG!! ( AS IF I CARE DUHH!! )Parental Guidance Is Needed

Some freaking rumours and spoilers:

Spoiler Alert! Click to show or hide

Rumours or Spoilers? Plz dun say this are all true! O.o

☆ Nunally and Sayoko were saved from the blast by Charles. Saving Nunally was intentional, Sayoko just happened to be there.

☆ Suzaku goes insane after he realizes what he has done. He prepares a strike against Britannia with the Lancelot and eliminates many of the lesser-important Knights. He is stopped by a mysterious Knightmare who identifies themselves as Knight of Zero. He is then captured and brought to Charles.

☆ Anya confronts Jeremiah and says that she believes she is under the influence of a Geass. Jeremiah takes her to Lelouch who confines her and then permits Jeremiah to use his Geass Canceler. It is then revealed that Anya is Lelouch’s true sister, and not Nunally. Lelouch does not believe it, but Jeremiah attempts to focus on Charles’ type of Geass within Lelouch’s mind, and finds it deeply hidden. His true past memories have no knowledge of Nunally.

☆ Nunally is the Knight of Zero, a special-ops Knight. She was (willingly) under Charles’ Geass to help advance his plans. She also has a Geass, identical to the one in the Nightmare of Nunally manga.

☆ The Black Knights initially betray Lelouch, after they see him going insane after the “death” of Nunally. After it is revealed that they are all key pawns in Charles’ plans, they agree to fight alongside Lelouch again

☆ Every major character, aside from Charles and Nunally, ally with Lulu to take down Britannia. They willingly accept Geass from Lulu, to help him launch a sneak attack against Charles, which ends up in failure, and the death of C.C. at the hands of Nunally.

☆ Before her death, C.C.’s inner soul speaks to Lulu with the mentality of her previous self. She encourages Lulu to continue on, and grants him her Code (immortality) and through a loophole, allows him to retain his Geass.

☆ Lelouch launches an immediate second attack on Britannia, and begins to be defeated again. However, his Geass overloads, and the effects of his Geass spread across the entire planet, affecting everyone he has never Geassed, telling them to “Destroy Britannia” - the world begins a full frontal assault on Charles and Nunally.

☆ Charles and Nunally’s primary goal is to “kill the gods”, by using a powerful cannon known as Loginus, to break through the dimensional barrier separating the two realms of life and afterlife. The Loginus is powered by human souls, and the power of Geass is able to amplify the charge for each soul. Those who die by the power of Geass, only further Charles’ plan.

☆ By killing the gods, Charles will be able to reform the world in a way that he sees fit. His vision of a new world? A world where no one has to suffer, and he can keep Nunally safe and happy, the same dream Lelouch had.

☆ The climax of the series ends with a battle between Lelouch, Anya, Suzaku and Kallen VS Charles and Nunally. Anya kills Nunally (with Suzaku and Kallen’s aid) and Lelouch forces Charles into the ray of the Loginus, utterly destroying him.

☆ After the series, Lelouch shuts himself off from the world, so he can no longer hurt anyone or see anyone be hurt. Suzaku, Anya and Kallen help reform the new world.

Spoiler Alert! Click to show or hide

Episode 20:
-Lelouch questions himself the reason he is fighting for, the memories of CC haunt his mind.
-Kallen decides to follow her heart and follows Lelouch in Guren. The ensuing conversation makes her realize Lelouch will never love her, but she decides to do whatever to make him truly happy.
-Suzaku is confronted by Lloyd about his true will. Lancelot Albion is introduced.
-Schneizel declares a coup d’etat against Charles. The nobles attach to him and while Ragnarok soars the sky he forcefully declares himself Holy Emperor by ordering the massacre of the entire royal family to his special forces. He declares his empire the New Holy Republic Of Britannia.
-Plans an assault on Ragnarok, to stop Charles’ plans
-Charles orders his closer knights to fight against Schneizel. Knights of Round fly to his aid.
-The episode ends with Suzaku’s choice of bringing down Britannia. He declares that a massacre is now inevitable.
-The Order of the Black Knights becomes Schneizel new group of dogs.

Episode 21:
-Anya is an important part of the Emperor’s plans, she is the one that carries “Marianne’s Memories”.
-Gino allies himself with Schneizel forces
-CC recovers her memories thanks to Lelouch’s passion. CC talks to Lelouch about Marianne’s demise, Charles’ true objectives and the reality behind Geass.
-Lelouch decides to stop Charles, but to first defeat Schneizel and use Britannia’s army against his father.
-Lancelot Albion flies toward the Ragnarok, is encountered by Galahad

Episode 22:
-Narration is now by CC and Lelouch together
-Lancelot Albion is at first on a completely different level when compared to the Galahand, Ko1 unveils his closed eye to reveal a Geass.
-Ko1’s Geass allows the user to see the future. However, all it predicts is despair. Ko1 seals his own eye since he isn’t sure if the Geass itself only predicts or if it causes the tragedy to happen. He is now unstoppable and Suzaku can’t touch him since he now predicts his movement.
-Orange arrives to help Suzaku. He talks to him about loyalty, not to your ideals but to those you love. He ungeasses him and Anya, and tells him to run away. To look in his heart for the answer. Orange is ultimately killed by the Galahand.
-Kallen must fight the Black Knights.
-Episode ends with Lelouch killing Schneizel, becoming the new Emperor of Britannia as he is the only living member of the Royal Family.

Episode 23
-Narration is still by Lelouch and CC
-Cornelia confronts Lelouch about Euphie.
-At the end of the episode, Lelouch and CC are nowhere to be found.

Episode 24
-Narration is by Suzaku
-Suzaku’s past is detailed in this episode. His ancient lover is revealed.
.-Nunally is still alive, teleported by the Charles alongside Sayoko and Rosenmeyer
-At the end of the episode, Lelouch and CC appear behind the Charles. “Check”, he says.

Episode 25
-Narration is by Nunally
-Anya confronts Charles.
-Suzaku inherits Charles code. Brings Ragnarok to the bottom of the ocean, thinks to himself that he will remain there dormant in Lancelot only to awaken when a new catastrophe surfaces.
-Lelouch and CC
-Nunally becomes Empress of Britannia as the only living heir.

''Predictions and Theories
Here are predictions and theories regardingthe finale and Season two, since Sunrise is going to make us wait forever anyway.

1. Why was Kallen so incredibly shocked at seeing Lelouch's face?

Kallen hates Britania. Although she went to a Britania school, she wasn't really associate with many people leave alone the men. Her Britania father wasn't there for her, and her mother is a real pain. And her borther she loved was killed by Britania as well. It is also that Kallen has this weird dream about Zero being her perfect guy. It happens that Luluche isn't really her type, so there... Who knows her type might be someone from Middle East or India and she was dreaming about that. - Anonymous

I believe Kallen was shocked because Lulu had been close to her the entire time, yet never trusted her enough to tell her and choose to lie to her and everyone else the entire time. In addition, the opinions he voiced in ep. 9 were relatively insulting and went against her own beliefs. Also, when he was unmasked, Lulu implied that he had used the BK and Kallen the entire time for his own gains and that the liberation of Japan (the reason the OoBK was founded on) was never his intention. He treated that as just a fortunate side-effect thus making it seem that Kallen and the others were simply his pawns the entire time. Imagine if the person that you trusted so much you would sacrifice yourself for in actuality had never viewed you more than a pawn and had lied to you the entire time. That about sums up how Kallen feels. Also, Lulu just HAD to follow that up with saying that he is the "the man who will obtain the world" -_-;;;;..... - lulu_quality

To say Kallen didnt expect Zero to be a Britannia is wrong, as Zero did mentioned before he is one. So maybe Kallen felt betrayed by Zero, that he used her? Maybe to Kallen, Zero is this perfect guy and lelouch isn't perfect enuff? Lol! P.S he is soooo perfect for me. - monstez

2. What is Cornelia's fate?

Cornalia's fate. Obviously she is not dead yet. More drama for S2. - Anonymous

Although I initially thought she was dead, as we didn't see concrete evidence of that. Instead I think she'll wind up in a coma or something from loss of blood. I wonder if she remembers Zero=Lulu though. She probably does, which makes me curious as to how she'll act on that information. - lulu_quality

I say we will still see Cornelia in Season 2, but not for long - she will die in episode 2 or something. - helenbutterfly

She is not shown nor mentioned dead, so there's a chance she is not. - monstez

I really hope that Cornelia will make it to season 2.>.> - nikki_chan_2006

3. What was/is Marianne planning?

I'm guessing whatever she is/was planning is related to the entire Ragnarok thing. Who knows what that is though. Maybe she wants Lulu to become the next emperor.... - lulu_quality

I'm not sure, what was Marianne planning, but I suppose it's something really good. And the plan obviously has a connection with C.C. - helenbutterfly

Something, but she is said to protect Nunally from the attackers, or was it part of her plot too? - monstez

4. How will Lelouch's and C.C.'s relationships change, or will they continue their (relatively) hostile and yet cooperative relationship?

I think they'll become much closer and more affectionate...in their own way. as that Black and White Nakie seacn and the kiss showed. - megami_tsuki

CC and Luluche? Well.. their relationship before ep 24+25 is identical to an old married couple. Now probably a newly wed again? Luluche x CC is obviously canon. With all the Official Art work, magazine covers, CD and story developments, you got to be lying to yourself if you aren't seeing it. She probably disappear for the first 3-4 episodes of the next season though. It also might be likely that she will be captured again. - Anonymous

I'm not the only one who thought the C.C.XLulu kiss was more like the kiss Misato gave to Shinji in EoE. I didn't really view the kiss as romantic, but more as an attachment/good luck kind of thing. Plus, how old is C.C. exactly -_-;;;; It's like dating your great, great, great.....(insert x number of greats here) grandmother, so it's hard for me at least to view their relationship as anything more than accomplices. Also in some interview, Yukana (I think it was) stated that after C.C. showed up at Lulu's house with no visible injury, Lulu stopped thinking of her as a human altogether. - lulu_quality

The end of Season 1 has showed that C.C. and Lelouch officially trust each other and are friends, because in the beginning there were too many doubts. I hope Lelouch realises that C.C. is the only one, who understands him and will always stay by his side. - helenbutterfly

Their relationship will definitely go deeper. You can see Lelouch's and C.C's face soften when they talk to each other in the end, like when she tell him to succeed and him telling her not to die. - monstez

I think that Lelouch && C.C. will be closer, but not into lover-relationship-mode...yet - nikki_chan_2006

5. Will Tokyo remain the same, will it be taken over by the Order or blown up by Nina?

Tokyo so gets blown up. It like an Anime rule or something... don't worry. they'll have it back up and running in like a week. - megami_tsuki

Nina is not gonna press the bomb (well, even if she did it won't went off). This thing is created by Sunrise, and Sunrise is a pussy for killing characters. They don't really dare making the plot awesome by killing popular characters. Unless there is some kind of "revival" or "time reset" crap going on, people in tokyo won't get blown up. Unless S2 was made by Gainax. - Anonymous

I can see Tokyo going along with Nina, but I can't see Nina as being the cause for that. Despite not being created by CLAMP, it does have some of their creative influences so I think Tokyo is going to go in true CLAMP fashion. - lulu_quality

In my opinion, it would be really cool to see Tokyo get blown up. XD But then again, for Tokyo becoming an empty space.. No, it should either remain the same or let it become a war place with many buildings being crushed. - helenbutterfly

The Order is pretty much beaten up after Zero left, unless Todoh can do another miracle, I'll say Tokyo is Britannia's. And I don't think Nina will blow it up. Lolyd is there to tell her not to. - monstez

6. Who shot and who got shot?

Obviously Kallen got shot by V.V. who is hiding in the shadow. "You are not needed Nee-san. I only need those two, the true Geass candidates." After that he teleport them up to the hall of twilight. Woot CLIMAX~(now I said this, Anonymous probably won't cover me up anymore). - Anonymous

I'm going to go with the idea that the shot wasn't actually a gunshot. Despite the Mr. 2chspoiler who stated that being a fake, it wasn't denied by the real Mr. Spoilers, which indicates that there might be some truth to that. - lulu_quality

Kallen shoots Suzaku and kills him pretty much. V.V. comes and makes a contract with Suzaku (I'm really going with this!) Lelouch gets out of the cave with Nunally, or V.V. kills Nunally and makes a contract with her instead of Suzaku. C.C. comes flying out of the ocean with Gawain after drowning Orange-kun and stealing an energy filler! xD - cr_balmung

I can't tell either one. I just saw Lulu placed that bomb thingy at his chest. (I hope no one gets shot.) - jay_kaou

Lelouch and Suzaku is screaming their lungs out, ready to shoot when.....
Kallen is so shocked that her gun accidentally misfire... A moment of silence, then Kallen goes..."SORRY!!!! Accident!!! Sorry!!"
Lelouch: You gave me a huge scare! I thought I was a goner!
Suzaku: Yea! I thought this moron shot me!
Lelouch: Well I could do that.
Suzaku: OO - monstez

who shot? ~~>Kallen
who got shot? ~~>suzaku (but of course..with the live geass thingeh, he'll live.>.>)
or
~~>nunally... - nikki_chan_2006

7. What is Villetta doing or going to do?

Villetta will either continue on her own looking up information on Lulu, or more likely, rejoin the Britannian military and impart this information. Also revenge. Lots of revenge. - lulu_quality

Ah, she will try to regain her position in Britannia military...Purist...Bah... - monstez

8. Do you think C.C. has a historical figure, if so, who would it be?

It was stated in one of the FO interview that; "All the connection will be clear one CC's name is revealed". From here we can pretty much assume that she at some point has a famous name, either historical or legendary. She however lost her memory, she don't really know what the hell she is. I am guessing that "Witch" was the name branded to her by the people during the witch hunt period. Her identity remains a secret. (Also if you were following FO QA since the starts of the series, you should know that she was a human who turn immortal after a certain event. more mystery). - Anonymous

There was a most probably fake spoiler stating that C.C. was Princess Elizabeth, Elizabeth of Bavaria, or something along those lines (although the timelines don't match at all), but I do think the possibility of her real name being Elizabeth, Narcissa, or Cecilia (as the nickname for both is Sissi/Cissi). C.C. did impart the info that she knew Benjamin Franklin in one of the drama CDs though, although she's definitely older than that. - lulu_quality

Somehow I see Jeanne D'Arc in C.C. D'Arc was burned and called a witch too. Also my theory would explain, why C.C. is cold on the outside and is a good fighter. - helenbutterfly
I think C.C is someone famous before or someone that is related to Lelouch? When Lelouch learnt of her name, he seems somewhat a little surprise, but also it may be because her name is nice? Lol! - monstez

All I think is..she has a connection with Marianne.x] - nikki_chan_2006

9. What will the main focus of Season 2 be?

I think the focus will be explaning more about the Geass and CC and VV and that mysterious place behind the door in the cave the stand off happened. - megami_tsuki

Another QA states that S2 will have increasing focus on Susaku, although the main focus will still be on Luluche." It is most likely the Black Knight VS Britania. Keep in mind that The Black Knight is NOT Japanese army. Zero intended to make it army of the world: Justice who protect the weak. We probably have Black Knight in other country pretty soon, moving out of the realm of Japan. - Anonymous

Taniguchi said in an interview that the 2nd season would move onto the world stage and talked about season 1 like it was a prologue to the events to come. I think it'll be a main focus, but will tie into the backstory/more information on the geass. In episode 19, it was revealed that the appearance of shrines like those on Kaminejima may be how the path of conquest is determined, so I think that will come into play. - lulu_quality

I think there won't be Season 3. All questions will be solved in S2. Lelouch is going to kick Emperor's butt. I have a feeling Emperor also has some kind of connection with Geass. L!Geass VS E!Geass? XD - helenbutterfly

I think the second series might focus at Suzaku and he might investigate about the Geass. - jay_kaou

I see season 2 trying to close all the plots, may unravel who is C.C, whats her name, Zero main focus may be getting to the emperor, I don't see him taking over the world, I mean he pratically bail out on the Order, will they forgive him? Not forgetting that Kallen knows that he used them as pawns... - monstez''

someone said it was like Sayako or something filling in his place either at the academy or at the the mobile base... i don't see how the one at the acadamy is possible without cutting hair and profession cosmetics... but i really don't have any idea.
''Apparently a magazine has stated that Sayako is impersonating Lelouch at Ashford Academy while he's in China and is also hitting on all the girls on campus.'' this may be a joke but who knows...
is the pic lol..
also maybe he just somehow flew back and forth really fast xD, but i doubt that... something is definetely amiss

well the most popular theory currently is tt sayoko has impersonated lelouch so lelouch will nt be suspected of regaining his memories bt who noes?? i have a feeling they are gonna put another twist on us..

Just guessing here but if Marianne was a witch then could the reason Nunnaly not open her eyes be because
she recieved a geass from her?
As far as i know the only reason she doesnt open her eyes was due to psychollogical trauma
at the time she and her mother were shot.